A known door lock apparatus for a vehicle is disclosed in U.S. 4762348. The electric door lock system disclosed in the above patent includes a box-shaped case member to which a rotating plate having a substantially circular shape is supported. The rotating plate can be driven in a clockwise direction and a counterclockwise direction by a motor. An output member having a fan shape is connected to one side face of the rotating plate. When the motor is driven to rotate the rotating plate in the counterclockwise direction by an operation of a relay in response to the operation of the inside switch by the user for opening the door, the output member pulls a rod for opening the door via an arm. Then, a pawl is rotated in a direction in which the engagement between the pawl and a latch is disengaged. The latch is subsequently rotated to an open position of the door and the unlock operation is completed accordingly. Meanwhile, when the motor is driven to rotate the rotating plate in the clockwise direction by operations of a half-latch sensor and a relay in response to the closing operation of the door to the half-latched position, the output member pulls a rod for closing the door via the other arm. Then, the latch is rotated to a full-latched position, and the door lock operation is completed accordingly. A neutral position sensor whose contact is retained in closed state by a circumferential face of the rotating plate is provided in the case member. When a concave portion formed on the other side face of the circumferential face of the rotating plate is moved to a portion where the neutral position sensor is positioned by the rotation of the rotating plate, the contact of the neutral position sensor becomes in the open state. The rotating plate is constituted to return to the neutral position side by the motor so that the rotating plate can start the following lock operation, for example, in case that the unlock operation is performed. When the contact of the neutral position sensor is turned in the open state with the concave portion being positioned at the neutral position sensor, the motor is stopped by the operation of the relay to prepare for the following operation (same return operation is performed in case of the lock operation).
According to the above-mentioned disclosed door lock apparatus, however, the following problems may occur. The motor is stopped based on the switching of the neutral position sensor to the open state when the rotating plate is returned to the neutral position at a time of the completion of the lock operation or the unlock operation. Thus, if the concave portion is set short in length in the circumferential direction of the rotating plate for precisely defining the neutral position, the neutral position sensor tends to be positioned out of the concave portion when the rotating plate overruns with the motor and then the standby state is initiated in that state. In this case, the neutral position sensor is in the closed status even if the door is open. This fails to satisfy the condition that all sensors are in open state under the door being open, which is disclosed in the above Japanese Publication. The lock operation is possibly not performed since the relay is not operated and thus the motor is not supplied with power even if the half-latch sensor becomes in the closed state by the door being closed to the half-latched position. Further, if the concave portion is set longer in length in the circumferential direction of the rotating plate so that the neutral position sensor is positioned within the concave portion even by the overrun of the motor, the neutral position range becomes too wide. This may cause the output member to start pulling the rod for unlocking the door, for example, when the rotating plate is returned to the neutral position upon completion of the lock operation, or the delay of the lock operation or the unlock operation to start. Especially when the user operates the inside switch for opening the door and therefore the rotating plate is rotated in the counterclockwise direction, first the neutral position sensor is required to reach one end portion from the other end portion of the long concave portion. Then, when the neutral position sensor becomes positioned out of the concave portion by the rotation of the rotating plate, the output member finally starts the unlock operation. Accordingly, a relatively long time-lag may occur until the door is actually opened, thereby causing the user to feel uncomfortable. In order to obtain the certainty of each operation, the length of the concave portion, within which the neutral position sensor remains to be positioned even by the overrun of the motor, cannot be surely defined by matching the length of the concave portion to the overrun of the motor that is objectively predicted. The predicted length is further required to be multiplied by a safety factor.
Thus, a need exists for a door lock apparatus for a vehicle which can surely perform the lock operation and the unlock operation. Further, a need exists for the vehicle door lock apparatus for the vehicle that can decrease a time-lag from the command signal output to a start of the lock operation or the unlock operation with a simple structure to thereby provide a more comfortable feeling to the user.